Plese tell me more about acquired immunity to malaria?

hey guys.. its a well known fact that even after 2 centuries of the discovery of the deadly and extremely potent disease... malaria... science has still not been able to make a breakthrough with a malalial vaccine... however it has been observed in a few regions in africa and asia that periodic and consistent exposure to the plasmodium can establish immunity in the affected person... any one wit any further information in dis regard pls do post ur thoughts... and let us help make a breakthrough dis century!